It is well establised that dietary protein causes calciuria. We have shown that a high protein diet induces hypercalciuria, and thereby a negative calcium balance, in both humans and laboratory animals. The negative calcium balance occurs even in the presence of adequate calcium intakes, and has potential significance for the development of ossteoporosis and periodontal disease in occidental populations which consume large amounts of dietary protein. We propose to use animal models to determine the short-term effect of high protein diets on calcium metabolism and bone calcium turnover, and their long-term effect on bone calcification and periodontal disease. Our preliminary research indicates that dietary protein impairs the fractional reabsorption of calcium by the kidney. We propose to investigate the mechanism by which this occurs in both human subjects and animal models.